I'm only going to answer one of your questions here. 3) I have visibly grainy negatives, and prints made from them, from FP4+ developed in monobath developer. It seems the fixing action mobilises the silver, so the grains get "replated" faster than they are dissolved. I have since heard of a monobath developer that uses ammonium thiosulfate, which does not increase grain. The "classical" sodium thiosulfate developer does - in my experience.